I don't thik 0.40 is correct for #1. For #2, I'm not sure what it is asking?
#1.
n = PV/RT = 3.5*4/0.08206*298, then
grams = mols x molar mass. I get something like 1.1 or so. You need to do it a little more accuartely than that.

#2. Could be asking for "What T in celsius is needed to obtain a pressure of 5.5 atm?"
T(in kelvin) = PV/nR = 5.5*4/0.08206*0.572
Then 273+C = K and solve for C.

You would do well to post NEW questions as a new question and not tag it to one already answered. Why? Because we often check for new questions before we go back to the older ones; therefore, it COULD get overlooked.
Here is a worked example of how to calculate theoretical yield.
http://www.jiskha.com/science/chemistry/stoichiometry.html